O-(2, 4, 5-trichlorophenyl) s-(ethylxanthoyl) dithiophosphoric chloride



Patented Feb. 9, 1954 -(2,4,5 TRICHLOROPHENYL) S --(ETHYL- XANTHOYL)DITHI OPHOSPHORIC CHLO- RIDE Henry Tolkmith, Midland, Mich., assignor toThe Dow Chemical Company, Midland, Mich., a

corporation of Delaware No Drawing. Application April 21, 1953, SerialNo. 350,247

1 Claim.

1 The present invention is directed to 042,4,5- trichlorophenyl)S-(ethylxanthoyl) dithiophosphoric chloride of the formula Cl Oi Thiscompound is a viscous oil, somewhat soluble in many organic solvents andsubstantially insoluble in water. It is of value as an intermediate forthe preparation of more complex phosphorus derivatives and as a toxicconstituent of parasiticide compositions.

The new compound may be prepared by reacting an alkali metalethylxanthate with O-(2,4,5- trichlorophenyl) thiophosphoric dichlorideof the formula in an inert organic solvent such as benzene orchloroform. Of the alkali metal xanthates found useful in the reaction,it is preferred to employ the sodium compound. Good results are obtainedwhen substantially equimolecular proportions of the reactants areemployed.

In carrying out the reaction, the sodium ethylxanthate is added withstirring to the O-(2,4,5- trichlorophenyl) thiophosphoric dichloridedispersed in the solvent and the resulting mixture heated for a periodof time at a temperature of from 35 to 80 C. If desired, the reactionmay be carried out in the presence of a small amount of a tertiary-aminesuch as triethyl amine as re action catalyst. Temperatures substantiallyin excess of 80 C. for any appreciable period of time should not beemployed as the desired product has a tendency to decompose at suchtemperature. Upon completion of the reaction, the mixture may befiltered and the filtrate distilled under reduced pressure at graduallyincreasing temperatures to separate low boiling constituents and toobtain as a residue the desired O-(2,4,5-trichlorophenyl)S-(ethylxanthoyl) dithiophosphoric chloride.

The O-(2,4,5-trichlorophenyl) thiophosphoric dichloride employed as astarting material in the above-described method may be prepared byreacting one molecular proportion of sodium 2,4,5- trichlorophenolatewith at least one molecular proportion of phosphorus thiochloride(193013) in an inert organic solvent such as benzene. In carrying outthe reaction the sodium 2,4,5-trichlorophenolate is added portionwisewith stirring to the phosphorus thiochloride and the resulting mixturethereafter heated for a period of time at a temperature of from 30 to C.to complete the reaction. The reaction is somewhat exothermic and takesplace smoothly at the temperature range 01" from 30 to C. Thetemperature may be controlled by regulation of the rate of contactingthe reactants as well as by the addition and subtraction of heat, ifrequired. Upon completion of the reaction, the mixture may be filteredand the filtrate fractionally distilled under reduced pressure to obtainthe desired O-(2,4,5-trichlorophenyl) thiophosphoric dichloride.

The latter is a viscous oil having a density of 1.6653 at 20 C. and arefractive index n/D of 1.6084 at 20 C.

In a representative preparation, 48 grams (0.33 mole) of sodiumethylxanthate was added with stirring to grams (0.303 mole) ofO-(2,4,5-trichlorophenyl) thiophosphoric dichloride and 3 grams oftriethyl amine dispersed in 250 milliliters of chloroform and theresulting mixture heated for 6 hours at a temperature of 50 C. At theend of this period, the reaction vessel and contents were cooled to roomtemperature and the reaction mixture filtered. The filtrate was thenWashed with water and thereafter concentrated by distillation underreduced pressure to a temperature up to 45 C. to obtain as a residue anO-(2,4,5-trichlorophenyl) S-ethylxanthoyl) dithiophosphoric chlorideproduct. The latter is a viscous oil having a density of 1.500% at 20 C.and a refractive index n/D of 1.5922 at 20 C.

The new O-(2,l,5-trichlorophenyl) S-ethylxanthoyl) dithiophosphoricchloride product is effective as a parasiticide and adapted to be employed for the control of a wide range of agricultural and householdpests such as flies, mites, aphides, beetles and cockroaches. For suchuse, the compound may be dispersed on an inert finely divided solid andemployed as a dust. Also, such mixtures may be dispersed in water withthe aid of a dispersing and wetting agent and the resulting aqueoussuspensions employed as sprays. In other procedures, the new product maybe employed in oils, as a constituent in oil in water emulsions, or inwater dispersion with or without the addition of emulsifying, wetting ordispersing agents. Suitable concentrations of the toxicant in dusts arein the order of from about 0.1 to 10 percent by weight of the dust andin liquid suspensions from about 0.1 to 3 pounds per 100 gallons of thespray mixture.

In representative operations against flies and cockroaches 100 percentkills of these pests are obtained with dust compositions containing 4.5percent by weight of the toxic dithiophosphoric chloride.

This is a continuation in part of my copending application Serial No.203,781, filed December 30, 1950.

I claim:

O-(2,4=,5 trichlorophenyl) S-(ethylxanthoyl) 10 dithiophosphoricchloride.

HENRY TOLKMITH.

No references cited.

